The present invention relates to an open top refrigerated display case having a storage portion. As the terms are used within this application, all references to refrigeration apparatus or operations are intended to include cooling both at temperatures in excess of 32.degree. F., for example, in fresh meats display cases and temperatures below 32.degree. F., for example, in frozen foods display cases.
In order to enable an open top refrigerated display case to be readily restocked as the need arises, a lower storage portion can be provided within such cases. Such an arrangement can be easily carried out since at least part of the bottom portion of such cases are usually unused because the depth of the interior of the display portion of the case must be limited in order to enable the consumers to readily obtain access to the products within the display portion. Thus, open top refrigerated display cases, which also include well type display cases, are provided with an upper display portion in which the refrigerated products are displayed for access by the consumer and a lower storage portion in which refrigerated products can be stored for readily restocking the display portion of the case.
Since refrigerated products are held in both the display portion and storage portion of the display case, both sections of the case must be appropriately cooled. A variety of different arrangements of cooling systems have been employed for such purposes within prior art systems. Possibly the most common of such systems have been those which merely circulate cool air throughout the entire case with air passing between the display portion and the storage portion of the case through a grating or similar structure, separating the display and storage portions. Typical of such arrangements are those illustrated in U.S. Pat. Nos. 2,306,969 to MacMasters, 2,348,988 to Lowell and 2,425,473 to Hoffman. The refrigerated display cases illustrated in all three of these patents are of the type where the refrigerated products can be viewed through windows in the front of the case while access to the displayed products are obtained through doors in the rear of the case; such display cases are typically utilized in delicatessan counters where an employee is present to assist the consumer.
Open top refrigerated display cases, i.e. where access to food contained within the display portion is obtained through an opening in the top of the case, which have lower storage sections are illustrated in U.S. Pat. Nos. 2,290,647 to Lowell, 2,631,438 to Weber and 3,226,945 to Spencer. In the patent to Lowell, a system is illustrated where the air circulating fan and refrigeration unit are provided within a chamber at the bottom of the case on one side of a lower storage section. Air is circulated by the fan through the refrigeration coils, which are both located within the chamber in the bottom of the case and such refrigerated air partially passes into the storage section and the remainder travels a path upwardly into the display section of the case. In the patents to Weber and Spencer, a continuous band of refrigerated air is established with an air curtain being provided across the opening in the display portion of the display case in order to protect the products within the case. Another patent which illustrates a refrigerated case with a storage section but instead of a top opening having a front opening therein is U.S. Pat. No. 2,476,491 to Henderson.
In the operation of all types of refrigerated display cases, it is desirable to include a system capable of automatically defrosting the display case. The defrost cycle can be actuated either at set periodic times or when the frost buildup within the system has reached a certain predetermined level. Such systems are typically thermostatically controlled so as to switch from a refrigeration cycle to a defrost cycle of operation. By this manner of operation, it is possible to avoid any significant frost buildup within the display case.
Typically within the prior art, there have been three different approaches employed for defrosting refrigerated display cases. The first approach involves the use of electric resistance heaters that are arranged adjacent to the refrigeration coils of the refrigeration mechanism. During a defrost cycle, these heaters supply in an effort to eliminate the frost buildup on the coils; however, the heaters also add warmer air to the air conduit for circulation within the case. During such a defrost cycle, the fans for circulating air through the primary conduit, i.e. the conduit in which the coils are located, can be turned off as disclosed in U.S. Pat. No. 3,756,038 to MacMaster et al. The particular technique is relatively simple both in its construction and operation. These electrical heaters are high wattage heaters that utilize significant electricity during operation. Furthermore, the warm air circulated in the case can raise the temperature of the case too high. Thus, attempts have been made to find alternatives to such a system.
A second type of system circulates compressed gaseous refrigerant through the refrigeration coils during the defrost cycle. During the defrost cycle, a valve control mechanism shuts off the supply of refrigerant to the refrigeration coils and alternatively feeds compressed gaseous refrigerant through the coils. This gas serves to reduce any frost buildup that has occurred on the refrigeration coils but simultaneously provides heat within the air conduit which can be circulated through the display case, which again is disadvantageous. Due to the requirement that the system be able to selectively switch between the supply of the gas for defrosting and refrigerant to the refrigeration coils, a valving structure must be provided. Such a mechanism increases the cost of construction of the system. In addition, the provision of such a system increases the number of parts capable of breaking down thereby necessitating costly repairs.
The third type of system employed for defrosting display cases relies upon ambient air. It is this general category with which the invention of the present application is concerned. One type of system that employs ambient air during the defrost cycle is exemplified by those embodiments illustrated in U.S. Pat. Nos. 3,403,525, 3,850,003 and 3,937,033, all to Beckwith et al. These systems use fans separate and distinct from the main air circulating fans. These extra fans are only turned on during the defrost cycle for pulling ambient air from outside of the display case directly into the air conduits. A second type of system is illustrated in U.S. Pat. No. 3,082,612 to Beckwith, which system draws ambient air into the main circulation path through ports located in the lower front panel of the refrigerated display case. Such ports are normally closed during the refrigeration cycle and are opened during the defrosting cycle. The Beckwith et al. U.S. Pat. No. 3,850,003 indicates that the concepts described in U.S. Pat. Nos. 3,082,612 and 3,403,525 did not prove to be practical and hence were not commercially feasible.
Finally, a third type of ambient air defrosting system is shown in U.S. Pat. No. 4,144,720 to Subera et al., which is assigned to the same assignee as the present application. In the foregoing patent application, an open front refrigerated display case having primary and secondary air conduits is disclosed. In this system, the direction of airflow within one of the conduits is reversed, for example by the use of reversible fans for ambient air defrost. Other patents illustrating ambient air defrost systems are U.S. Pat. No. 4,026,121 to Aokage, which illustrates an open front display case, and U.S. Pat. No. 4,120,174 to Johnston, which illustrates an open top display case.